Due to the recent energy problems that have arisen, considerable interest has been given to converting the kinetic energy of wind into electrical power, e.g., using wind-power generation systems (e.g., that are sometimes called wind-energy conversion systems). For example, some wind-energy conversion systems involve wind flowing through a turbine located atop a substantially vertical tower so that the turbine rotates an electrical generator in response to the wind flowing through the turbine. This causes the electrical generator to produce electrical power.
Such turbines are typically complex machines that may have several sub-machines that convert the kinetic energy of the wind to electrical power. That is, these machines may have a large number of moving parts that are subject to failure and that may require considerable maintenance, resulting in high maintenance costs.
In particular, the power generation depends on the length of the turbine blades, e.g., the longer each turbine blade, the higher the power generation. However, long blades can be costly, take up a large amount of space, and may generate excessive noise and vibration. Longer turbine blades may increase not only the cost of material and installation, but may also increase the cost of maintenance. As such, some current wind-energy conversion systems may suffer from low efficiency, high capital cost, high maintenance costs, and/or unacceptably high noise and vibration.
Turbines with relatively long blades may operate at relatively low rotational speeds (e.g., typically 20 rpm for wind turbines) and may require gears to increase the rotational speed up to rotational speeds that are useful for the generator (e.g., typically 1500 rpm for a 1.5 MW generator). This may involve high levels of torque and accompanying high gear-mesh forces that can cause the gears to fail, thus meaning considerable maintenance to reduce the amount of failures. Because of the low speed of the turbine, the various gearbox components are usually supported by rolling element bearings. These bearings are subject to significant radial loads that can cause the bearings to fail prematurely, thus meaning considerable maintenance to reduce the amount of failures.
Some wind-energy conversion systems may include a yaw system for turning the turbine into the wind. For example, a yaw system may include a motor (e.g., a yaw motor) coupled to a turbine-generator assembly by drive, such as a yaw drive, that may include a gear system. The yaw motor activates the yaw drive that in turn rotates the turbine-generator assembly so that the turbine faces into the wind. However, yaw systems may be complex and expensive, can fail, and may require considerable maintenance. Yaw systems may also be difficult to access, in that they are usually located adjacent to the turbine-generator assembly atop a tower.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternatives to existing wind-energy conversion systems.